The woofer cone will sag a bit and assuming it doesn't have a very long linear excursion (most old woofers do not) the result could be audible distortion setting in at a lower volume level. As long as it has 2-3" clearance above the floor it can breathe just fine.
No harm in trying what you describe, but now drivers that you were supposed to listen to on-axis will be off-axis and vice versa. If the design was highly optimized for the normal orientation, sound qualiy will be degraded.
No harm in trying what you describe, but now drivers that you were supposed to listen to on-axis will be off-axis and vice versa. If the design was highly optimized for the normal orientation, sound qualiy will be degraded.